I would click "View Reservation" and look at the top of your page. You should see a similar statement:

This reservation was ticketed and confirmed on Fri., Dec. 2, 2016 at X:YZ p.m. Central Time.

The two times never differ more than 0-1 minutes for me, but to be safe I'd go with the reservation time if you're not sure or if the statement above is not there.